The BGS Lexicon of Named Rock Units — Result Details

Torridge Valley Formation

The formation encompasses the fluvial, lacustrine and organic deposits of the River Torridge and its tributaries. It includes floodplain alluvium and the deposits of eight river terraces. The floodplain alluvium comprises soft poorly sorted clays, silts and fine-grained sands, with bodies of peat, overlying sands and subrounded gravels. The terrace deposits dominantly comprise silty and sandy pebbly clays but include sands and gravels and silts. The clays are largely derived from Upper Carboniferous mudstone bedrock. Gravels are dominantly formed of rounded pebbles up to 50mm in diameter of Upper Carboniferous sandstone but also include vein quartz and Lower Carboniferous limestone and chert. Boulders of Dartmoor Granite and quartz-feldspar-tourmaline rock are common in the upper reaches of the River Okement and its tributaries. The terraces contain alluvial tin ore (cassiterite).

Definition of Lower Boundary:

Unconformable upon bedrock of Early and Late Carboniferous and Permian age and upon the Dartmoor Granite.

Definition of Upper Boundary:

Surface.

Thickness:

To c.10m

Geographical Limits:

The entire catchment of the River Torridge and its tributaries, including the rivers Okement and Waldon, between Dartmoor and Bideford, Devon.

The valley of the rivers Torridge and Okement from Dartmoor to Bideford, Devon. Freshney et al., 1979.

Reference(s):

Freshney, E C, Beer, K E and Wright, J E. 1979. Geology of the country around Chumleigh. Memoir of the Geological Survey of Great Britain, Sheet 309 (England and Wales).

Freshney, E C, Edmonds, E A, Taylor, R T and Williams, B J. 1979. Geology of the country around Bude and Bradworthy. Memoir of the Geological Survey of Great Britain, sheets 307 and 308 (England and Wales).